Pay-station automatic telephone system



Ayn-i122; 1924. 1,491,338

R. D. CONWAY PAY STATION AUTOMATIC TELEPHONE SYSTEM Filed Feb. 19. 1921 2 Shee'ts-Sheet l /nven7or: Ray D. Conway.

April 22 1924.

R.D.CONWAY PAY STATION AUTOMATIC TELEPHONE SYSTEM Filed Feb. 19. 1921 2 Sheeis-Sheet 2 //7 van for.-

Patented Apr. 22, 1924.

UNITED STATES PATENT OFFICE. I

ROY D. CONWAY, OF CHATHAM, NEW JERSEY, ASSIG-NOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PAY-STATION AUTOMATIC TELEPHONE SYSTEM.

Application filed February 19, 1921. Serial No. 446,391.

To all whom it may concern.

Be it known that I, ROY D. CONWAY, a citizen of the United States, residing at Uhatham, in the county of Morris, State of New Jersey, have invented certain new and useful Improvements in Pay-Station Auto matic Telephone Systems, of which the followingis a full, clear, concise, and exact description.

This invention relates to machine switch ing telephone exchange systems with subscribers control wherein coin collectors are provided at the substations.

One of the objects of this invention is to provide an improved circuit arrangement for systems of this type which shall be positive and efiicient in operation, and which shall require no change in the standard dial or coin collector now most generally employed.

Another object is to permit the calling party to build up a connection to certain lines and carry on a conversation without having to deposit a coin, as for example on fire calls or calls to an operator.

A further object is to provide an'arrangement wherein the coin is not collected unless the conversational circuit between the parties is actually established. In accordance with this invention, a polarized relayin the trunk at the central ofiice is included in circuit with the calling line, and operates due to a reversal in the direction of the current flow in the calling line when the called party answers and operates a disconnect relay at the central ofiice which opens the trunk conductors. The operation of the polarized relay connects a relay in circuit with the calling line to test for the presence of the coin in the coin collector. The deposit of the coin connects the polarized magnet in the coin box to ground from one side of tho line, and the test relay operates due to the presence of this ground. In operating, this relay causes the release of the disconnect relay which reconnects the trunk conductors to permit conversation to be carried on. Due to the operation of the polarized relay and the test relay, a circuit is closed when the calling subscriber replaces his receiver including a source of current of one polarity which circuit includes the calling line to operate the polarized magnet in the coin box to collect the coin. If thefirst impulse fails to collect the coin, additional impulses are transmitted, and the connection is held to the coin control equipment untilthe coin is collected.

If the called line is busy or the called party fails to answer, the replacement of the receiver causes a source of current'o-f the opposite polarity to be applied to the calling line to operate the polarized magnet in the coin box in the opposite direction to refund the coin, whereupon the connection is released. I

Inasmuch as the connection is opened at the central ofiice only due to a reversal of the current flow in the calling line by the response of the called party, this invention provides an arrangement whereby certain lines may be segregated on connectors which do not reverse the current upon the response of the called party and consequently conversation may be carried on without the necessity of depositing a coin.

Referring tothe drawings, Fig. 1 shows a calling line, a line switch, and the coin control circuit; Fig. 2 shows a secondary line switch, a selector, connector and a called line. I

The invention will be most readily unde stood from a detailed description of the operation of the system.

Upon removal of the receiverat the calling substation A, relay 100 of the primary line switch PLS individual to the calling line is operated over the calling line circuit. In attracting its armature it closes a circuit including the pull down winding 101 of the line switch which causes the line switch to seize the preselected trunk by operating the set of springs shown, in the well-known manner, as described in detail in Patent No. 1,304,369 to A. J. Ray, issued May 20, 1919. When the primary line switch PLS operates and closes springs 102 and 103, the following circuit is closed to operate the secondary line switch SLS to seize an idle first selector FS; grounded spring 102, spring 103, secondary line switch holding conductor 104C, inner left-hand armature and back contact of relay 105, conductors 106, 201, 202, pull down coil 203 of the secondary line switch, contact 204, conductor 205, relay 206, free pole of battery. The secondary line switch in operating closes a locking circuit for itself including its windings 207, 203 in series, and contact- 208 to ground on holding conductor 201. Only parts of the apparatus of the first selector and connector C are shown since these switches are well-known, see Reissue Patent No. 13,901, issued April 13, 1915, to F. Newforth. The calling party now operates his sender 107 to set these switches in the Well-known manner.

lVhen the connection has been built up to the called line, the response of the called party operates relay 211 which reverses the flow of current in the tip and ring conductors leading back to the calling line, to operate polarized relay 108 in the coin control circuit. hen the selector FS was seized the release wire 235 was grounded thereat in the well-known manner to operate relay 109. This relay at its innermost right armature grounded release wire 112 connected to the holding winding 148 of the primary line switch to hold the same set after the relay 100 is cut off as the line switch operates. Relay 109 also operated slow relay 113. When the connector C is seized the impulse relay 210 operates and energies slow relay 240, which in attracting its left-hand armature holds ground on the release conductor 237 to hold operated the release relay of the selector FS and relay 109 in the coin control circuit.

when the relay 108 operates upon the response of the called party, relay 110 operates over the following circuit: free pole of battery, resistance 153, relay 110, its in ner left-hand armature and back contact, contact of polarized relay 108, conductors 111, 112 to ground at the innermost right armature of relay 109. Relay 110 restores the original connections of the relay 210 to the tip and ring conductors in the connector to prevent the coin ground from interfering with the release of the switches when the, calling subscriber hangs up his receiver as will appear hereinafter. Relay 110 in closing its contact 114 locks itself to groundedconductor 112, and also operates relay 115 over the following circuit: free pole of battery, relay 11,5, conductor 11.6, middle right-hand armature and front contact of relay 109, conductor 117, outer right armature and back contact of slow to operate relay 118, conductor 119, contact 114 to grounded conductor 112. Relay 115 in attracting its arn'iature 120 locks itself to ground over the following circuit: free pole of battery, relay 115, armature 120, conductor 121, outer right-hand armature and back contact of relay 118, contact 114 of relay 110 to grounded conductor 112. Relay 115 in operating closed a bridge 162 across the tip and ring conductors to hold up the selector and connector and connects the test relay-122 to the tip and ring of the calling line and if the contact 123 in the coin collector is closed, which will be the case if the coin has been deposited, relay 122 operates over the following circuit; free pole of battery, outer right armature and back contact of relay 105, conductor 124, outer left armature and front contact of relay 109, relay 122, conductor 125, alternate contacts of relay 115, closed contacts of the primary line switch in multiple over the tip and ring conductors, contact 123 of the coin collector to ground, through the polarized magnet 126 of the coin collector. The coin collector may be of the type shown in Patent No. 1,043,219, issued November 5, 1912, to O. F. Fosberg. Relay 122 in operating closes the following circuit for slow-to-operate relay 118; free pole of battery, relay 118, contact 126 thereof, conductor 127, outer left armature and front contact of relay 110, conductor 128, inner right armature and back contact of relay 105, conductor 129, armature and front contact of relay 122,- conductor 130, inner left armature and front contact of relay 109 to ground. Relay 118 in closing its contact 131, locks itself to ground at the lower armature and front contact of relay 113, and prepares a circuit from the source of collect current CC to the calling line. Relay 115 is released by relay 118 operating and reconnects the calling line tip and ring conductors to the tip and ring conductors of the trunk to permit conversation to be carried on.

Talking current is fed to the calling line over the following circuit; free pole of battery, right-hand winding of relay 210, outer armature and front contact of relay 211, conductor 231, multiple 229, brush 228 of the selector 8, conductor 227, contact 226 of the secondary line switch SLS, tip conductors 225, 133, contact 134 of relay; 110, ring conductor 135, armature 136 of relay 115, ring conductor 137. contact 138 of the primary line switch, ring conductor 139 through the transmitter of the calling line returning over the tip conductor 140, contact 141 of the primary line switch, tip conductor 142, armature 143 of relay 115, tip conductor 144, contact 145 of relay 110, ring conductor 146, ring conductor 232, contact 216 of the switch SLS, ring conductor 215, brush 214, multiple 213, of the selector S, conductor 233, inner ari'i'iature and front contact of relay 211. left-hand coil of relay FS and relay 109 whichthereupon release the former releasing the selector and the latter operating relay 105 over the following circuit; outermost armature and back contact of relay 109, relay 105 to ground at lowermost armature and front contact of slow relay 113. Before relay 113 which is slow, can release, when its original circuit is opened as relay 109 releases, a substitute circuit is provided for it as follows; inner right armature and front contact of relay 105, conductor 129, armature 147 and back contact of relay 115, relay 113, free pole of battery. Relay 105 in attracting its inner left-hand armature, opens the holding conductor 106 leading to the secondary line switch SLS, which thereupon releases. The primary line switch is held however, due to the maintained energization of relay 113. The upper armature of this relay is applying current to conductor 112 which is connected to the holding winding 148 of the primary line switch. when the interrupting machine 149 next reaches a metallic segment, the relay 109 is operated in a circuit including contact 150 of relay 105. Relay 109 in attracting its middle right armature operates relay 115 over the following circuit; free pole of battery, relay 115, conductor 116, middle right armature and front contact of relay 109, inner left armature and front contact of relay 105, conductor 104, contacts 103, 102 to ground. When relay 109 operated it again closed the original circuit of relay 113. Relay 115 in attracting its armature looks over the following circuit; free pole of battery, relay 115, armature 120, conductor 121, inner left armature and front contact of relay 105 to grounded conductor 104. \Vhen the interrupting machine 149 reaches the next insulating segment, it releases relay 109 which closes the following circuit to operate the polarized magnet 26 in the coin box at the calling station to collect the coin; source of collect positive current, left armature and front contact of relay 118, outer left armature and back contact of relay 109, relay 122, conductor 1.25, armature 143 and front contact of relay 115, tip conductor 142, contact 141 of the line switch, conductor 140, contact 123 of the coin collector, polarized magnet 126 to ground. Relay 122 closes a circuit to hold up slow relay 113, this circuit including the inner right armature of locked up relay 105. The next operation of relay 109 disconnects the collect current causing magnet 126 to open contact 123. If the coin is not released by the first impulse, although the relay 122 retracts its armature, the relay 109 operates from the interrupter before the slow-relay 113 gets time to release after its circuit is opened by the release of relay 122, and conductor 112 is thus held grounded preventing the release of the primary line switch. Due to the failure of'the magnet 126 to collect the coin at the first impulse the relay 122 again operates when the relay 109 again releases, from the coin ground, providing a substitute circuit for slow-relay 113 as before to hold the primary line switch set. lVhen the coin is collected and contact 123 opened, the next time the interrupting machine 149 reaches an insulating segment and releases relay 109, the failure of relay 122 to operate causes the release of the slow relay 113 which in retracting its upper armature removes ground from the conductor 112 connected to the holding winding148 of the primary line switch causing its release. Relay 113 in releasing its lowermost armature releases relay 105 which in opening its contact 150 disconnects the interrupting machine from the relay 109. The retraction of the inner left armature of relay 105 opens the locking circuit of relay 115 which thereupon releases. The retraction of the lower armature of relay 113 also releases relay 118. The retraction of the upper armature of relay 113 unlocks the relay 110. The apparatus is now restored to its normal condition.

The function of the relay 110 which operates when the called subscriber answers is to connect the tip or side of the trunk which is grounded at the coin collector to the ring side of the line which is connected to the grounded side of the coil 21.0, to prevent the coin ground from holding up the connection after the calling subscriber has hung up his reciver and the called subscriber still has his removed.

If the called subscriber hangs up first, polarized relay 108 will operate and short circuit the relay 110 to restore the tip side which is connected to ground at thecoin collector to the tip side of the trunk, which is normally connected to ground through the left-hand coil of relay 210 to prevent the coin ground from holding up the connection upon the replacement of the receiver by the calling party.

The function of the condenser 152 and resistance 153 is to provide a discharge path to prevent sparking at the back contact of the outer left armature of relay 109 as the relatively high potential coin current circuit is broken.

The function of the induction coil 53 is to transmit a tone from the tone coil 155 of the calling line to the operator in case the calling subscriber selects an operator instead of an automatic subscriber.

It will be apparent that in order for relay 118 to operate and prepare the collect circuit, relay 110 must be operated when the coin is inserted, since the circuit for operating relay 118 includes the out-er left armature and front contact of relay 110, and the front contact of the coin test relay 122. Now if the called party responds and hangs up before the calling party deposits the coin, this coin will be refunded when the calling party hangs up since relay 110 released when the called party replaced his receiver and therefore although the relay 122 operated due to the deposit of the coin and closed one break in the circuit of relay 118, the circuit is open at the outer left armature of relay 110.

The relay 110 should be so constructed as to cause the armatures 14:5 and 160 to make their front contacts before the armature 161 makes its front contact in order to give the polarized relay 108 sufficient time to operate and open its contact before the armature 161 has closed its front contact long enough to shunt the winding of the relay 110 when the called party answers.

hat is claimed is:

1. In a machine switching telephone system, the combination with a temporarily established connection including a pair of subscribers lines, trunks, and automatic switches, means including a relay at the central office operated by the response of the called party for opening said connection, a coin collector at the calling station, means operated by the deposit of a coin therein for causing a circuit change in the substation equipment, a test relay at the central oflice connected to the calling line upon the response of the called party and operated due to a circuit change, means operated by said test relay for reclosing said connection, a source of current for operating said coin collector, means controlled over one of the subscribers lines to release the connection, and means thereupon automatically operated to connect said current to said coin collector to collect the coin.

2. In a machine switching telephone systerm the combination with a temporarily established connection including a pair of subscribers lines, trunks, and automatic switches, a relay at the central office operated by the response of the called party for opening said connection, a coin collector at the calling station, means operated by the deposit of a coin therein for causing a circuit change in the substation equipment, a test relay at the central oflice connected to the calling line upon the response of the called party and operated due to said circuit change, means operated by said relay for reclosing said connection, a circuit for operating said coin collector to collect the coin, and means for closing said circuit.

In a machine switching telephone system, the combination with a temporarily established connection including a pair of lines, trunks and automatic switches, a relay at the central office operated by the response of the called party for opening said connection, a coin collector at the calling station'adapted to be connected in a ground branch from one side of the line by the deposit of a coin, a test relay at the central oifice, a circuit therefor including said branch, closed upon the response of the called party, and means operated by said test relay for reclosing said connection.

at. In a machine switching telephone system, the combination with a temporarily established connection including a pair of lines, trunks and automatic switches, a relay at the central oflice operated by the response of the called party for opening said connection, a coin collector at the calling station adapted to be connected in a ground branch from one side of the line by the deposit of a coin, a test relay at the central otlice, a circuit therefor including said branch closed upon the response of the called party, means operated by said test relay for reclosing said connection, a circuit for operating said coin collector to collect the coin, and means for closing said circuit.

In a machine switching telephone system,'the combination with a temporarily established connection including a pair of lines, trunks and automatic switches, a relay at the central office operated by the response of the called party for opening said connection, a'coin collector at the calling station adapted to be connected'in a ground branch from one side of the line by the deposit of a coin, a test relay at the central ofiice, a circuit therefor including said branch closed upon the response of the called party, means operated by said test relay i or reclosing said connection, a circuit for operating said coin collector to collect the coin, and means for closing said circuit upon the replacement of the receiver by one of the parties.

6. In a machine switching telephone system, the combination with a temporarily established connection including a pair of lines, trunks and automatic switches, a relay at the central ofiice operated by the response of the called party for opening said connection, a coil collector at the calling station adapted to be connected in a ground branch from one side of the line by the deposit of a coin, test relay at the central ofiice, a circuit therefor including said branch closed upon the response of the called party, means operated by said test relay for reclosing said connection, a circuit for operating said coin collector to collect the coin, means for closing said circuit upon the replacement of the receiver by the calling party.

7. In a machine switching telephone system, the combination with a temporarily established connection including a pair of subscribers lines, trunks and automatic switches, and a polarized relay operated upon the response of the called party, a relay at the central oliice operated thereby to open said connection, a coin box at the calling station, means controlled by the deposit of the coin for causing said relay to reclose said connection, a circuit for operating said coin collector to collect the coin, and means for closing said circuit.

8. In a machine switching telephone system, the combination with a temporarily es tablished connection including a pair of subscribers lines, trunks and automatic switches and a polarized relay operated upon the response of the called party, a relay at the cen tral ofi lce operated thereby to open said connection, a coin box at the calling station, means controlled by the deposit of the coin for causing said relay to reclose said connection, a circuit for operating said coin collector to collect the coin, and means for closing said circuit upon the breaking of the connection.

9. In a machine switching telephone system, the combination with a temporarily established connection including a pair of subscribers lines, trunks and automatic switches and a polarized relay operated upon the response of the called party, a relay at the central office operated thereby to open said connection, a coin box at the calling station, means controlled by the deposit of the coin for causing said relay to reclose said connection, a circuit for operating said coin collector to collect the coin, and means for closing said circuit upon the replacement of the receiver by the calling party.

10. In a machine switching telephone system, the combination with a temporarily established connection including a pair of subscribers lines, trunks and automatic switches and a polarized relay operated upon the response of the called party, a relay at the central office operated thereby to open said connection, a coin box at the calling station, means controlled by the deposit of the coin for causing said relay to reclose said connection, a circuit for operating said coin collector to collect the coin, and means for closing said circuit and for holding a part of the connection until the coin is collected. I

11. In a machine switchin telephone system, the combination with calling and called telephone lines, trunks and automatic switches, a coin collector at the substation of the calling line having a magnet adapted to collect or refund the deposited coin, senders for said lines, means operated by the deposit of a coin for causing a circuit change in the substation equipment, a polarized relay'at the central ofiice operated upon the response of the called party, a disconnect relay operated thereby for opening the established connection, a test relay connected to the calling line'by the operation of said disconnect relay, and operated due to said circuit change, said relay reestablishing said connection, a circuit including a source of current of one polarity prepared due to the response of the called party, and means responsive to the replacement of the receiver by the calling party for closing said prepared circuit including the calling line to operate said magnet to collect the coin.

12. In a machine switching telephonesystem, the combination Withcalling and called telephone lines, trunks and automatic switches, a coin collector at the substation of the calling line having a magnet adapted to collect or refund a deposited coin, senders for said lines, means operated by the deposit of a coin for causing a circuit change in the substation equipment, a polarized relay at the central office operated upon the response of the called party, a disconnect relay operated thereby for opening the established connection, a test relay connected to the calling line by the operation of said disconnect relay, and operated due to said circuit change, said relayestablishing said connection, a circuit including a source of current of one polarity prepared due to the response of the called party, means responsive to the replacement of the receiver by the calling party for closing said prepared circuit including the calling line, to operate said magnet to collect the coin, and means for holding said circuit closed until the coin is collected.

13. In a machine switching telephone system, the combination with a temporarily established connection including a pair of subscribers lines, trunks and automatic switches, means including a polarized relay at the central oflice operated by the response of the called party for opening said connection, a coin collector at the calling station adapted to be connected in a ground branch from one side of the line by the deposit of a coin, a test relay at the central oflice, a circuit therefor including said branch closed upon the response of the called party, means operated by said test relay for reclosing said connection, a source of collect current at the central oflice, a circuit therefor prepared by the operation of said polarized relay, means for subsequently closing said circuit to operate the coin collector to collect the coin, a source of refund current, and a circuit therefor including the calling line closed to operate said coin col lector to refund the coin if the called party,

has not responded.

14. In a machine switching telephone system, the combination with a temporarily established connection, including a pair of subscribers lines, trunks and automatic switches, means including a polarized relay at the central ofiice operated by the res ponse of the called party for opening said connections, a coin collector at the calling station adapted to be connected in a ground branch at one side of the line by the deposit of a coin, a source of collect current, a circuit therefor prepared by the operation; of said polarized relay, and means for applying said current to the calling line to operate said coin collector upon the breaking down of the connection.

15. In a machine switching telephone system, the combination with a temporarily established connection, includig a pair of subscribers lines, trunks and automatic switches, means including a polarized relay at the central ofi'ice operated by the response of the called party for opening said connection, a coin collector at the calling station adapted to be connected in a ground branch on one side of the line by the deposit of a coin, a test relay connected to the calling line by theoperation of the polarized relay and operating due to the closure of said branch to reclose said connection, a source of collect current, a circuit therefor including the coin collector prepared by the response of the test relay and closed upon the breaking down of the connection, a source of refund current, a circuit therefor prepared by the failure of the polarized relay to operate, and means for applying said current to the calling line to operate said coin collector to refund the coin upon the breaking down of the connection.

16. I11 a machine switching telephone exchange system, the combination of a temporarily established connection, including a pair of subscribers lines, trunks, and automatic switches, a relay at the central office operated only when certain lines are called, for opening said connection, a coin collector at the calling station, means operated by the deposit of a coin therein for causing a circuit change in the substation equipment, a test relay at the central ofiice connected to the calling line upon the responseof the called party and operated due to said circuit change, means operated by said test relay for reclosing said connection, a circuit for operating said coin collector to collect the coin, and means for closing said circuit.

17. In a machine switching telephone exchange system, the combination of a temporarily established connection, including a pair of subscribers lines, trunks, and automatic switches, a polarized relay operated upon the response of the called party only when certain lines are selected, a disconnect relay at the central ofiice operated thereby to open said connection, a coin box at the calling station adapted to be connected in a ground branch from one side of the line at the substation by the deposit of a coin, a test relay at the central office, a circuit therefor including said branch closed upon the operation of said disconnect relay, means operated by said test relay for reclosing said connection, a circuit for operating said coin collector to collect the coin, and means for closing said circuit.

18. In a machine switching telephone exchange system, the combination, of a temporarily established connection, including a pair of subscribers lines, trunks and automatic switches, a polarized relay operated upon the response of the called party only when certain lines are selected, a disconnect relay at the central oli ice operated thereby to open said connection, a coin box at the calling station adapted to be connected in a ground branch from one side of the line at the substation by the deposit of a coin, a test relay at the central office, a circuit therefor including said branch closed upon the operation of said disconnect relay, means operated by said test relay for reclosing said connection, a circuit for'operating said coin collector to collect the coin, and means for closing said circuit upon the replacement of the receiver by the calling party.

19. In a machine switching telephone system, the combination of a temporarily established connection including a pair of subscribers lines, trunks, and automatic switches, a polarized relay at the central oilice operated by the response of the called party for opening said connection only when certain lines are selected, a coin collector at the calling station adapted to be connected in a ground branch from one side of the line by the deposit of a coin, a test relay at the central office closed upon the operation of said polarized relay, means operated by said test relay for reclosing said connection, a source'of collect current at the central oflice prepared by the operation of said polarized relay, means for subsequently closing said circuit to operate the coin collector, a source of refund current, and a circuit therefor including the calling line closed to operate said coin collector to refund the coin if the called party does not respond.

20. In amachine switching telephone system,the combination with a temporarily established connection including a pair of subscribers lines, trunks and automatic switches, a relay at the central oflice operated by the response of the called party for opening said connection, a coin box at the calling station, means operated by the deposit of a coin therein for causing a circuit change in the substation equipment, a test relay at the central oiiice connected to the calling line and operated due to said circuit change, and means jointly operated by the response of the called subscriber and the operation of said test relay for causing said coin collector to collect the coin.

21. In a machine switching telephone system, the combination with a temporarily established connection including a pair of subscribers lines, trunks and automatic switches, a relay at the central ofiice operated by the response of the called party for opening said connection, a coin box at the calling station, means operated by the deposit of a coin therein for causing a circuit change in the substation equipment, a test relay at the central oifice connected to the calling line and operated due to said circuit change, means jointly operated by the response of the called subscriber and the operation of said test relay for causing said coin collector to collect the coin, and a circuit for controlling the application of current of one polarity to operate said coin box to collect the coin, closed only if the called partys line is closed when said test relay operates.

22. In a machine switching telephone system, the combination with a temporarily established connection including a pair of subscribers lines, trunks and automatic switches, a relay at the central office operated by the response of the called party for opening said connection, a coin box at the calling station, means operated by the deposit of a coin therein for causing a circuit change in the substation equipment, a test relay at the central oflice connected to the calling line and operated due to said circuit change, means jointly operated by the response of the called subscriber and the operation of said test relay for causing said coin collector tocollect the coin, and a circuit for applying current of the opposite polarity to refund the coin, closed if the called line is open when the test relay operates.

23. In a machine switching telephone system, the combination with a temporarily established connection including a pair of subscribers lines, trunks and automatic switches, a relay at the central office operated by the response of the called party for opening said connection, a coin box at the calling station, means operated by the deposit of a coin therein for causing a circuit change in the substation equipment, a test relay at the central oflice connected to the calling line and operated due to said circuit change, means jointly operated by the response of the called subscriber and the operation of said test relay for causing said coin collector to collect the coin, a circuit for applying current of the opposite polarity to refund the coin, closed if the called line is open when the test relay operates, and means for closing the coin current cir cuit upon the breaking down of the con nection.

In witness whereof, I hereunto subscribe my name this 15th day of February A. D.,

ROY D. CONWAY. 

